1. Field of the Invention
This invention relates generally to optical broadcast switches and, more particularly, to a splitterless optical broadcast switch for communication and data handling satellites.
2. Discussion of the Related Art
The exploding demand for global wireless communications, data gathering and signal processing is currently placing unprecedented requirements on the capabilities of communication and data handling satellites. These satellites include single platform communication systems which operate independently from other systems, multi-platform communication systems which employ many cross-linked satellites, and data handling systems which sense and monitor various parameters. This demand is dramatically increasing signal traffic which is leading to saturation of existing RF bands that have been allocated for the various communication functions. Such saturation is increasing the need to utilize new frequency bands at much higher frequencies.
As a result, future communication and data handling satellites will be required to process very wide bandwidths comprised of densely populated signals. Moreover, these satellites will need to provide frequency conversion capabilities to route signals through different allocated bands assigned by different international regulatory agencies. However, the use of current satellite RF signal interconnects and distribution systems have several disadvantages.
For example, existing communication and data handling satellites are limited by the characteristics of RF coaxial cables. In other words, signals received and transmitted by the satellites, via its antenna, are interconnected and distributed throughout the satellite on coaxial cables. Coaxial cables are inherently large, bulky and heavy transmission mediums. Moreover, coaxial cables are designed to operate in a specific frequency band and are thus substantially band limited. Still further, coaxial cables tend to exhibit very high losses as the frequency increases.
The above-identified disadvantages associated with the use of coaxial cables is further amplified by its use in satellites. Specifically, the losses exhibited with coaxial cables require the satellite to have additional amplifiers which requires larger power supplies, which in turn requires more solar panels to supply the energy to the system. The weight and size of the satellite is also significantly increased because of these losses, as well as because of the size and weight of the coaxial cables. This increase in weight and size also ultimately increases launch costs of the satellite. Still further, since coaxial cables are bandwidth limited, a greater number of coaxial cables are required to handle various frequency bands the satellite may operate at. This causes the satellite to be less versatile at handling multiple frequency bands.
A photonic interconnect and photonic processing apparatus for communication and data handling satellites reduces or eliminates the above mentioned disadvantages. This in turn, increases bandwidth capabilities; increases versatility; decreases weight and size of the satellite; decreases power consumption; decreases launch costs; and decreases the overall cost of communication and data handling satellites. While the photonic interconnect and photonic processing apparatus for communication and data handling satellites is an improvement over existing prior art systems, the optical switching employed by the photonic interconnect photonic processing system may also be further improved upon.
For example, many M input.times.N output optical broadcast switches employ power splitters to obtain broadcast capability. Use of such power splitters creates optical split loss which may become a problem when high dynamic range or a low noise floor is required. To overcome the losses incurred by the use of optical power splitters, optical amplifiers can be employed. However, these optical amplifiers generally require extremely high optical saturation power levels when placed before split losses to maintain high dynamic range. For satellite applications where DC power consumption is important, this approach may be undesirable due to its potential inefficient use of optical power and associated DC power. Moreover, introduction of the optical amplifiers further introduces additional noise into the system thereby further raising the noise floor. Such M.times.N optical broadcast switches must also generate enough optical power to support MN outputs, even though only N of the signals are actually used. This situation arises because a laser source in a photonic network is generally paired or coupled directly to a particular optical modulator and RF input irrespective of the network switching configuration.
What is needed then is a splitterless optical broadcast switch for communication and data handling satellites, as well as for terrestrial based applications, which eliminates the use of power splitters to obtain broadcast capability. This will, in turn, further decrease the weight and size of the satellite; further decrease power consumption and need; further decrease launch costs; reduce overall noise within the system; and pair each laser source with a photodetector instead of with an optical modulator and the RF input. It is, therefore, an object of the present invention to provide such a splitterless optical broadcast switch.